In large pipelines, such as 36-inch pipelines, it is conventional to use a large rotating ball element to open and close the valve. Such ball valves require a high torque to close the valve and also require a considerable amount of time to close the valve, which is undesirable in emergencies.
The present invention is directed to a pipeline valve which may be quickly closed in an emergency in which the valve element moves coaxially in the valve body for seating, is actuated by a plurality of piston and cylinder assemblies, and which has a minimum restriction to fluid flow.